No need to worry,
Price increases
When we increase subscription prices, existing subscribers are unaffected by default; they are placed into a legacy price cohort where they continue to pay their original base plan price when they renew.
If the existing user cancels or pause there subscriptions, And later in future if they subscribe again then latest prices will be applied & charged.
So you can continue you subscriptions without any worry of price change.
Price decreases
When you end a legacy price cohort and the new price is lower than the price that users in the cohort are paying, Google Play notifies the users by email and these subscribers begin paying the lower price the next time they pay for their base plan.
End a legacy price cohort
You can choose to end a legacy price cohort at any time. This can be done independently for each region. To end a legacy price through the Play Console, refer to the Play Console Help Center.